1. Field of the Invention
The present invention relates to a throttle opening degree sensor mounted to a throttle body provided with throttle valve for opening and closing an intake passage, by which a potentiometer rotates in connection with a throttle valve, and an electric voltage signal is output in proportion to an opening degree of the throttle valve. The opening degree sensor mentioned above is used for detecting the opening degree of the throttle valve which controls an amount of air in a fuel injection apparatus or detecting an opening degree of the throttle valve of a carburetor for adjusting an amount and a concentration of an air-fuel mixture supplied to an engine.
2. Description of the Conventional Art
An example of a conventional throttle opening degree sensor is shown in FIGS. 3 and 4.
FIG. 3 is a side view in the state that the throttle opening degree sensor is mounted to a throttle body.
FIG. 4 is a vertical cross sectional view of a main portion in a line A—A in FIG. 3.
A description will be given with reference to these drawings.
Reference 10 denotes a throttle body in which an intake passage 11 is provided through. A throttle shaft 12 is transversely arranged within the intake passage 11, the throttle shaft is rotatably supported to a throttle shaft hole 10A of the throttle body 10, and the intake passage 11 is opened and closed by a butterfly type throttle valve 13 attached to the throttle shaft 12. The throttle shaft 12 crosses over the intake passage 11 and is rotatably supported to the throttle shaft hole 10A provided in the throttle body 10, and in the drawings, a left throttle shaft hole 10Aa is open onto a left end surface 10B of the throttle body 10 via a guide hole 10C having a larger diameter than the throttle shaft hole 10Aa. The throttle valve 13 in FIG. 3 is in the state of closing the intake passage 11, and the throttle valve 13 rotates in a clockwise direction in FIG. 3, to open the intake passage 11.
Reference symbol S denotes a throttle opening degree sensor, which is constituted of the following elements.
Reference numeral 14 denotes a casing, within which a rotor 15, a brush (not shown) fixed to the rotor 15, a resistance body (not shown) provided in a fixed member and slidably contacted by the brush and the like are received and arranged. A pair of one side mounting flange portion 14B and another side mounting flange portion 14C are integrally formed in the side of a flat right side surface 14A in the right side in FIG. 4 in the casing 14 so as to be directed toward one side C and another side D orthogonal to a longitudinal axial line B—B of the rotor 15, and mounting holes 14D are pieced through the respective mounting flange portions 14B and 14C.
Further, a guide tube portion 14E is formed in the right side surface 14A of the casing 14 so as to be coaxial with the longitudinal axial line B—B of the rotor 15 and as to slightly protrude to the right side E, and a clearance hole 14H is provided from a front end 14F of the guide tube portion 14E toward a rotor supporting hole 14G rotatably supporting the rotor 15. That is, the rotor supporting hole 14G is open to the front end 14F of the guide tube portion 14E via the clearance hole 14H.
Further, an annular seal ring groove 14J positioned outside the guide tube portion 14E is recessed in the right side surface 14A of the casing 14.
Further, the throttle opening degree sensor S is assembled with the throttle body 10 in the following manner.
The throttle opening degree sensor S is arranged on the left end surface 10B of the throttle body 10.
In accordance with the structure mentioned above, the right side surface 14A of the casing 14 is arranged in the left end surface 10B of the throttle body 10 so as to contact therewith, the mounting hole 14D of one side mounting flange portion 14B is arranged so as to face to one side screw hole 10G open to the left end surface 10B of the throttle body 10, the mounting hole 14D of another side mounting flange portion 14C is arranged so as to face to another side screw hole 10D open to the left end surface 10B, the guide tube portion 14E is inserted into and arranged within the guide hole 10C of the throttle body 10, and a flat portion 12A formed in a left end of the throttle shaft 12 is inserted into and arranged within a flat groove 15A provided in the rotor 15 and open toward the right side E.
Further, in the state mentioned above, screws 16 are inserted into the respective mounting holes 14D of one side mounting flange portion 14B and another side mounting flange portion 14C, and the screws 16 are screwed toward one side screw hole 10G and another side screw hole 10D, whereby the throttle opening degree sensor S is engaged by screwing with and fixed on the throttle body 10, and on the other hand, the throttle shaft 12 and the throttle opening degree sensor S are connected by the flat portion 12A and the flat groove 15A so as to synchronously rotate.
In accordance with the structure mentioned above, when the throttle valve 13 opens and closes the intake passage 11 on the basis of the rotation of the throttle shaft 12, the rotation of the throttle shaft 12 is transmitted to the rotor 15 from the flat portion 12A via the flat groove 15A, and the brush fixed to the rotor 15 slides on the resistance body provided in the fixed member in correspondence with the rotation mentioned above, whereby the throttle opening degree sensor S outputs an electric voltage signal corresponding to the rotation of the throttle shaft 12 toward the external.
In accordance with the conventional throttle opening degree sensor mentioned above, the throttle opening degree sensor S is assembled on the throttle body 10 via one side mounting flange portion 14B and another side mounting flange portion 14C, and since a pair of the mounting flange portions 14B and 14C are provided as mentioned above, it is impossible to make the throttle opening degree sensor S itself compact and in particular, a mounting property of the throttle body onto a motor cycle of a small or middle class piston displacement (for example, 90 cc, 120 cc, 250 cc or the like) is impaired, so that it is not preferable.
The reason for the necessity to provide with a pair of the mounting flange portions 14B and 14C as mentioned above is that there is not provided with a means for securely preventing the throttle opening degree sensor S from falling down at a time of arranging the throttle opening degree sensor S on the throttle body 10.
The guide tube portion 14E shown in FIG. 4 has a function for simply positioning sideward, and even in the case that the guide tube portion 14E is inserted into the guide hole 10C of the throttle body 10, it can not constitute a means for preventing the throttle opening degree sensor S from falling down off the longitudinal axial direction B—B.
Further, because a pair of the mounting flange portions 14B and 14C are provided, it is necessary to provide with two screw holes 10G and 10D in the throttle body 10, it is necessary to prepare two screws 16 and it is necessary to carry out a screwing operation at two times, resulting in an increase of number of parts and an increase of number of assembling man-hour, so that it is prevented a manufacturing cost of the throttle body from being reduced.
Further, in the throttle body 10, it is necessary to provide with bosses of supporting portions 10E and 10F facing to the mounting flange portions 14B and 14C, resulting in an increase of weight of the throttle body 10, and an increase of a thick portion which generates blow holes at a time of injection molding of the throttle body 10, so that it is not preferable. In particular, the supporting portions 10E and 10F facing to the mounting flange portions are formed near the left throttle shaft hole 10Aa, the generation of the blow holes causes an intrusion of air into the left throttle shaft hole 10Aa from the outside, so that it is not preferable.
Further, an airtightness between the left throttle shaft hole 10Aa and an atmosphere, an airtightness between the inside of the throttle opening sensor S and the atmosphere are achieved by a seal ring 17 such as an O-ring, a square ring or the like made of an annular elastic material (for example, a rubber) arranged within a seal ring groove 14J provided in the right side surface 14A of the casing 14, whereby it is necessary to form an annular seal boss 10H having a diameter G sufficiently larger than an outside groove diameter F of the seal ring groove 14J in an outer periphery of the left throttle shaft hole 10Aa, thereby, similarly to the above mentioned, increasing a weight of the throttle body 10 and generating the blow hole at a time of injection molding of the throttle body 10, so that it is not preferable.